Disc drives are data storage devices that store digital data in magnetic form on a rotating disc. Modern disc drives comprise one or more rigid information storage discs that are coated with a magnetizable medium and mounted on the hub of a spindle motor for rotation at a constant, high speed. Information is stored on the discs in a plurality of concentric, circular tracks typically by an array of transducers (known as “heads”), which are mounted to a radial actuator for movement of the heads relative to the discs. During a write operation, sequential data is written onto a selected one of the disc tracks. During a read operation, the head senses the data previously written onto the disc track and transfers the information to an external environment. Important to both of these operations is the accurate and efficient positioning of the head relative to the center of the desired track. Head positioning within a desired track is dependent on head-positioning servo patterns, i.e., magnetic patterns recorded onto the disc surface and used to maintain optimum track spacing and sector timing. Servo patterns or servo information can be located between the data sectors on each track of a disc (known as “embedded servo” information), or on only one surface of one of the discs within the disc drive (known as “dedicated servo” information). Regardless of whether a manufacturer uses “embedded” or “dedicated” servo information, the servo patterns are typically recorded on the disc or discs during the manufacturing process of the disc drive.
Servo patterns are typically recorded on the magnetizable medium of the disc by a servo-track writer (“STW”) assembly during the manufacture of the disc drive. One conventional servo track writer assembly records servo patterns on the discs following installation of the discs into the disc drive. In this embodiment, the servo track writer assembly attaches directly to a disc drive having a disc pack, where the mounted discs on the disc pack have not been pre-recorded with servo patterns. The servo track writer essentially uses the drive's own read/write heads to record the requisite servo patterns directly to the mounted discs. An alternative method for servo pattern recording utilizes a separate apparatus having dedicated servo-recording transducers or heads for recording the servo patterns onto one or more of the discs prior to the discs being assembled into the disc drive. The dedicated servo recording heads can be used to record servo patterns to a number of discs simultaneously, which are subsequently loaded into the disc drive for use.
Recent efforts within the disc drive industry have focused on developing cost-effective disc drives capable of storing more data onto existing or smaller-sized discs. One potential way of increasing data storage on a disc surface is to increase the recording density of the magnetizable medium by increasing the track density (i.e., the number of tracks per millimeter). Increased track density requires more closely-spaced, narrow tracks and therefore enhanced accuracy in the recording of the servo-patterns onto the disc surface. This increased accuracy requires that servo-track recording be accomplished within increased tolerances, while remaining cost effective.
In light of the desire for increased accuracy in the writing of servo patterns, it has been found that vibrations in the servo track writer assembly caused by disc rotation, operation of the spindle motor, and actuator movement can result in inaccurate servo information being written to the disc surface. Inaccurate servo information limits the ability of the electromechanical actuator to accurately position the data head directly over the desired data track during normal track following operations.
Accordingly, there is a desire to reduce or eliminate vibrations during servo track writing operations such that improvements in servo pattern recording accuracy can be achieved. The present invention provides a solution to these and other problems, and offers other advantages over the prior art.